The present invention relates to an adapter device for field, i.e., remote, signals of computers, microprocessor systems or the like digital electronic circuits, said adapter comprising a rectifier unit for input signals, an ON-OFF voltage switching circuit operated by the input voltage, and an adapter circuit.
An adapting unit used in this type of adapter devices is generally an opto-isolator which comprises a light-emitting diode and a light sensitive transistor. In such a micro-component, the gaps, i.e., spacings, between connecting lines are usually not sufficient for the required (at least 3750 V) potential difference, i.e., to prevent arcing between adjacent conductors. One particular nuisance is the need to connect the adapter device not only to the input signal but also to a separate source of energy, since no significant energy can pass through the device, i.e., an opto-isolator. Another drawback in the prior art adapter devices is inadequate interference elimination, especially as far as the capacitive interference disturbances of field cables are concerned.
The main objective of this invention is to provide an adapter of the above type by means of which the energy of an input signal can be used for input or output control without external power sources and which is further capable of providing a sufficient isolation against large induced potential differences.